1. Field of the Invention
The present invention relates generally to connectors for joining butting tubing elements, more particularly to a system for forming high temperature, high pressure joints between adjacent open-ended tubes, particularly tubes formed from composite materials.
The formation of butt joints in open-ended tubing is problematic, particularly when the joint must withstand high working temperatures and pressures. Problems are exacerbated when the tubing is formed from materials which have a relatively low thread (shear) strength, such as plastic, ceramic, and/or carbon-carbon composites, which makes the formation of conventional threaded connections impractical. While compressible seals, such as O-ring seals, can be utilized to improve the sealing characteristics of the joint, composite materials are frequently not sufficiently strong to provide the desired compression of the seal ring when using conventional threaded end connectors. The O-ring materials generally used do not provide seals at high temperatures, i.e., above 500.degree. F.
It would therefore be desirable to provide connector designs, systems, and apparatus suitable for joining all types of open-ended tubing and pipes together. The connectors should be relatively simple to manufacture and to implement, and should be suitable for fabrication from most or all types of materials, including composite materials. It would be particularly desirable if the connectors could provide high strength coupling between tubes formed from materials possessing relatively low thread (shear) strength, even when all elements of the connector are formed from the same material. The connectors should include a compressible seal element between the tubes being joined and should be able to provide sufficient compressive (tightening) force to form an effective seal, even against high temperature and pressure. Preferably, the connectors should provide both axial and radial compression of the seal to provide for highly efficient joining of the separate tubing elements.
2. Description of the Background Art
Axially-split connecting structures having internal threads are disclosed in U.S. Pat. Nos. 4,236,736; 4,095,826; 3,352,575; and 1,283,554. The structure of the U.S. Pat. No. 4,095,826 is particularly intended for joining rigid plastic pipes. U.S. Pat. Nos. 4,613,161; 4,226,164; 4,159,132; 3,224,795; and 3,041,088, describe other systems for joining open-ended tubes together.